Primer composition and uses thereof

ABSTRACT

The present invention provides a primer for a thermoplastic and/or elastomeric substrate, the primer comprising a film of an epoxy-modified polymer selected from the group consisting of an epoxy-modified-thermoplastic polymer, an epoxy-modified-thermoplastic polymeric composite, an epoxy-modified-elastomeric polymer, an epoxy-modified-elastomeric polymeric composite, a blend thereof, and any mixture thereof. Also provided are methods of repairing, inserting, assembling and coating a thermoplastic or elastomeric substrate using the primer of the present invention.

CROSS-REFERENCE APPLICATIONS

This application claims the benefit of U.S. Provisional Application Ser.No. 60/572,758 filed May 21, 2004, which is herein incorporated byreference.

FIELD OF THE INVENTION

The present invention relates to a primer composition and uses thereof.In particular, the present invention relates to a primer comprising anepoxy-modified polymer selected from the group consisting of anepoxy-modified-thermoplastic polymer, an epoxy-modified-thermoplasticpolymeric composite, an epoxy-modified-elastomeric polymer, anepoxy-modified-elastomeric polymeric composite, a blend thereof, and anymixture thereof. The primer is useful in the repair, insertion, assemblyand coating of thermoplastic and/or elastomeric substrates.

BACKGROUND OF THE INVENTION

The low polarity (hydrophobicity) and inert characteristics of thesurface of many thermoplastic and elastomeric polymers, especiallypolyolefins (PO), cause many problems in the repair, assembly, insertionand coating of these polymers with the same or other materials,especially in structural applications. Hot-melt adhesives are oftenused, because they are able to penetrate into the polymer surface tocreate good fusion bonding with the polymeric matrix. To promote thefusion bonding process, heat-gun, hotplate, ultrasonic, vibration, andresistance welding may be applied. Alternatively, surface treatment byplasma, flame, or laser, which allows joining of parts by conventionaladhesives, is also sometimes used.

For hot-melt adhesives, heat-gun techniques are not sufficient forjoining large areas and it is very difficult to control the uniformityand reproducibility of the joint. In addition, when assemblingdissimilar materials, it is not always possible to find an adhesive thatprovides good bonding with both substrates. In hotplate welding, hightemperature is always required for good fusion bonding, and this is notalways easy to accomplish for large and/or thin parts with complexshape. Similarly, vibration and ultrasonic welding also presentdifficulties in joining large parts with complex shapes, and incontrolling fibre alignment. Furthermore, especially for PO composites,and especially in structural applications, strong enough adhesion isrequired to carry the load into/through the joint. Commercial hot-meltadhesives cannot sustain such high load levels while surface treatmenttechniques are not always practical in industrial applications.

Primers have been used in the past to improve adhesion between twosurfaces.

U.S. Pat. No. 6,344,500 issued on Feb. 5, 2002 to Ogawa et al. disclosesan aqueous primer coating composition comprising a blend of an acidanhydride-modified poly(olefin chloride) emulsion resin, an aqueousalkyd resin and an aqueous novolac-type epoxy resin for coating aplastic material to impart gasohol resistance.

U.S. Pat. No. 6,337,134 issued on Jan. 8, 2002 to Takai discloses aprimer composition for paint comprising a blend of 100 parts by weightof an epoxidized EPDM and 50 to 70 parts by weight of a product ofchlorination of a polyolefin modified with an unsaturated carboxylicacid or an anhydride thereof.

U.S. Pat. No. 6,494,983 issued on Dec. 17, 2002 to Graue et al.discloses a cured enamel coating for a metal surface comprising a solidsmixture of an epoxy resin, a phenolic resin, carboxy-polyolefin resinand polyester resin.

U.S. Pat. No. 6,497,337 issued Dec. 24, 2002 to Kehe discloses an enamelcomprising a blend of a cresol-formaldehyde/epoxy resin and maleicanhydride-modified polypropylene resin adhesion promoter.

U.S. Pat. No. 6,391,461 issued May 21, 2002 to Ryntz et al. discloses amethod of improving adhesion to thermoplastic olefins using an adhesionpromoter selected from the group consisting of a chlorinated polyolefin,a hydrogenated poly(butadiene)diol, and mixtures thereof.

There remains a need for an effective and easy to use primer for use inthe repair, assembly, insertion and/or coating of thermoplastic and/orelastomeric substrates, especially with other dissimilar materials like,for example, thermosets and their composites, thermoplastics and theircomposites, elastomers, metals, ceramics, wood, leather, fabrics, etc.For example, there remains a need for a primer particularly useful forproviding high bond strength in the repair, assembly and/or insertion ofthermoplastic and/or elastomeric composites.

SUMMARY OF THE INVENTION

In a first aspect, there is provided a primer for a thermoplastic and/orelastomeric substrate, the primer comprising a film of an epoxy-modifiedpolymer selected from the group consisting of anepoxy-modified-thermoplastic polymer, an epoxy-modified-thermoplasticpolymeric composite, an epoxy-modified-elastomeric polymer, anepoxy-modified-elastomeric polymeric composite, a blend thereof, and anymixture thereof.

In a second aspect, there is provided a method of repairing, inserting,assembling or coating a thermoplastic or elastomeric substrate, themethod comprising: applying to the substrate, a primer comprising a filmof an epoxy-modified polymer selected from the group consisting of anepoxy-modified-thermoplastic polymer, an epoxy-modified-thermoplasticpolymeric composite, an epoxy-modified-elastomeric polymer, anepoxy-modified-elastomeric polymeric composite, a blend thereof, and anymixture thereof; and, applying a repair, insertion, assembly or coatingmaterial to the primer.

In a third aspect, there is provided a method of repairing athermoplastic or elastomeric substrate, the method comprising: applyingto the substrate, a primer comprising a film of an epoxy-modifiedpolymer selected from the group consisting of anepoxy-modified-thermoplastic polymer, an epoxy-modified-thermoplasticpolymeric composite, an epoxy-modified-elastomeric polymer, anepoxy-modified-elastomeric polymeric composite, a blend thereof, and anymixture thereof; applying a thermoset resin or thermoset composite tothe primer on the substrate; and, setting the thermoset resin orthermoset composite.

In a fourth aspect, there is provided a method of assembling an article,the method comprising: applying to a thermoplastic or elastomericsubstrate, a primer comprising a film of an epoxy-modified polymerselected from the group consisting of an epoxy-modified-thermoplasticpolymer, an epoxy-modified-thermoplastic polymeric composite, anepoxy-modified-elastomeric polymer, an epoxy-modified-elastomericpolymeric composite, a blend thereof, and any mixture thereof; applyingan adhesive to the primer on the substrate, applying an assemblymaterial to the adhesive, and, setting the adhesive.

In a fifth aspect, there is provided a method of coating a thermoplasticor elastomeric substrate, the method comprising: applying to thesubstrate, a primer comprising a film of an epoxy-modified polymerselected from the group consisting of an epoxy-modified-thermoplasticpolymer, an epoxy-modified-thermoplastic polymeric composite, anepoxy-modified-elastomeric polymer, an epoxy-modified-elastomericpolymeric composite, a blend thereof, and any mixture thereof; and,applying a coating material to the primer to thereby coat the substrate.

In a sixth aspect, there is provided a method of repairing, insertingassembling or coating an article, the method comprising: placing athermoplastic or elastomeric substrate in a mold; placing a primercomprising a film of an epoxy-modified polymer selected from the groupconsisting of an epoxy-modified-thermoplastic polymer, anepoxy-modified-thermoplastic polymeric composite, anepoxy-modified-elastomeric polymer, an epoxy-modified-elastomericpolymeric composite, a blend thereof, and any mixture thereof in themold; placing a repair, insertion, assembly or coating material in themold; and, heating to form a molded article.

In a seventh aspect, there is provided an article of manufacturecomprising a polyolefin and a primer on the polyolefin, the primercomprising an epoxy-modified-carboxyl-grafted-polyolefin.

DETAILED DESCRIPTION

As used in the specification and the appended claims, the singular forms“a,” “an” and “the” include plural referents unless the context clearlydictates otherwise.

Primer:

The epoxy-modified polymer can be conveniently considered as comprisingtwo components: a thermoplastic or elastomeric polymer component and anepoxy-containing component attached to the thermoplastic or elastomericpolymer component. The primer may be a homopolymer, copolymer, blend ormixture thereof. The primer may be a composite comprising theepoxy-modified polymer and a reinforcing material for example, fibers,layered crystalline clays, particle fillers, whiskers, nanotubes,metallic oxides, metallic sulfides, metallic layered double hydroxides,or any mixture thereof.

Any suitable thermoplastic polymer may be used as the thermoplasticpolymer component. For example, some suitable thermoplastic polymersinclude, olefinics (i.e. polyolefins), vinylics, styrenics,acrylonitrilics, acrylics, cellulosics, polyamides, thermoplasticpolyesters, thermoplastic polycarbonates, polysulfones, polyimides,polyether/oxides, polyketones, fluoropolymers, copolymers thereof, orany mixture thereof. Polyolefins, polyamides and thermoplasticpolyesters are of particular note, for example, homopolymers,copolymers, terpolymers, or mixtures of polyolefins, polyamides andthermoplastic polyesters. Some suitable polyolefins include, forexample, polypropylene, polybutylene, polymethylpentene, polyethylenes(e.g., LDPE, HDPE, LLDPE, UHMWPE, XLPE, copolymers of ethylene withanother monomer (e.g., ethylene-propylene copolymer)), or any mixturethereof. Polypropylene and its derivatives are of particular note. Somesuitable thermoplastic polyesters include, for example, polyethyleneterephthalate, polycarbonate, polyetherketone, and biodegradablepolyesters such as polylactic acid (PLA), polyhydroxyalkanoate (PHA) andtheir geometric and optical (e.g. D and L) isomers.

Any suitable elastomeric polymer may be used as the elastomeric polymercomponent. For example, some suitable elastomeric polymers include,polyisoprene, polybutadiene, polychloroprene, polyisobutylene,styrene-butadiene rubber, acrylonitrile-butadiene rubber,ethylene-propylene rubber, ethylene-propylene-diene rubber, chlorinatedpolyethylene, chlorosulfonated polyethylene, ethylene-vinyl acetatecopolymer, ethylene-acrylate copolymer, fluoroelastomers (e.g.polyvinylidene fluoride, polytrichlorofluoroethylene), silicone polymers(e.g. polydimethylsiloxane), acrylic rubber, epichlorohydrin rubber,pulysulfide rubbers, propyleneoxide rubbers, polynorbornene,polyorganophosphazenes, olefinic thermoplastic rubbers, styrenicthermoplastic rubbers, urethane thermoplastic rubbers, etheresterthermoplastic rubbers, etheramide thermoplastic rubbers, or any mixturethereof.

The epoxy-containing component of the primer may be derived from anysuitable epoxy compound. Epoxy-containing components comprising one ormore glycidyl groups are of particular interest. Examples includeglycidyl methacrylate, glycidyl acrylate, glycidyl-2-ethyl acrylate,glycidyl-2-propyl acrylate, monoglycidyl itaconate, monoglycidylbutenetricarboxylate, diglycidyl butenetricarboxylate, glycidyl ester ofmaleic acid, glycidyl ester of crotonic acid, glycidyl ester of fumaricacid, alpha-chloroallyl glycidyl ester, diglycidyl ether of bis-phenolA, diglycidyl ether of p-aminophenol,N,N,N′,N′-tetraglycidyl-4,4′-methylene-bis-benzene amine,4-glycidyloxy-N,N′-diglycidylaniline, tetraglycidyl diamino diphenylmethane, diglycidyl ether of bis-phenol A novolac resin, epoxy phenolnovolacs, epoxy cresol novolacs, allyl glycidyl ether, methallylglycidyl ether, isopropenylphenyl-glycidyl ether, vinyl glycidyl ether,glycidyl oxyethylvinyl ether, styrene-p-glycidyl ether, p-glycidylstyrene, epichlorohydrin, polynuclear phenolepoxy, hydantoin epoxy, etc.Specific examples include EPON™ 1004 (a bisphenol A base epoxy resinfrom Shell Chemicals), EPON™ SU-3 (a bisphenol A and novolac base epoxyresin from Shell Chemicals), Araldite™ MY0510 (diglycidyl ether ofpara-aminophenol base epoxy resin from Vantico) and Araldite™ MY 727(N,N,N′,N′-tetraglycidyl-4,4′-methylene-bis-benzenamine base epoxy resinfrom Vantico).

The primer may be made by suitable reaction between a thermoplastic orelastomeric polymer and an epoxy compound. Grafting reactions in whichthe epoxy compound is grafted on to the thermoplastic or elastomericpolymer are of particular note. Alternatively, the epoxy compound may begrafted on to a monomer of a thermoplastic or elastomeric polymer andthe monomer then polymerized or copolymerized to form an epoxy graftedthermoplastic or elastomeric polymer. The epoxy compound may be graftedto a thermoplastic or elastomeric polymer or a monomer thereof eitherdirectly or through a coupling agent.

When the epoxy compound is grafted directly to the thermoplastic orelastomeric polymer, the epoxy compound must comprise a functional groupthat permits grafting to the polymer. Reference is made to Table 1 foran exemplary list for matching functional groups to some polymers. Oneskilled in the art will readily recognize other possible combinations.

TABLE 1 Polymer Functional group Polyolefins - homopolymers and Olefinicbond copolymers Polyamide Epoxide, hydoxyl, ester, acid Thermoplasticpolyester Epoxide, hydroxyl, phenol, ester, acid

When the desired epoxy compound cannot be directly grafted or isdifficult to graft to the desired polymer, a coupling agent is required.In this case, there are a variety of choices of coupling agent. Onefunctional group on the coupling agent permits grafting to thethermoplastic or elastomeric polymer while another functional group onthe coupling agent must be able to react with a functional group on theepoxy compound. Selection of a functional group for grafting to thepolymer is well within the ability of one skilled in the art, with Table1 providing an exemplary list for guidance. Selection of appropriatefunctional groups for reaction between the coupling agent and the epoxycompound is also well within the ability of one skilled in the art.Reference is made to Table 2 for an exemplary list for matching reactivefunctional groups between the coupling agent and the epoxy compound. Oneskilled in the art will readily recognize other possible combinations.

TABLE 2 Functional Group Functional Group on Coupling Agent on EpoxyCompound Vinyl Hydride Vinyl Alcohol Vinyl Alkyl halide Phenol Alkylhalide Isocyanate, Isothiocyanate Alcohol (hydroxyl) Acid chloridePhenol Acid chloride Alcohol (hydroxyl) Acid chloride Amide AnhydrideEpoxy Carboxylic acid Alcohol (hydroxyl) Ester Alcohol (hydroxyl)Carboxylic acid Epoxy Amide Acid chloride Alcohol (hydroxyl) VinylAlcohol (hydroxyl) Acid chloride Alcohol (hydroxyl) Ester Alcohol(hydroxyl) Carboxylic acid Amine Anhydride Amine Acid chloride AmineEpoxide Amine Carboxylic acid

Coupling agents with amine, hydroxyl, ester, carboxylic acid orcarboxylic acid anhydride functional groups are of particular note. Forexample, unsaturated carboxylic acids, unsaturated carboxylic acidanhydrides or mixtures thereof may be specifically mentioned. Somesuitable unsaturated carboxylic acids include, for example, acrylicacid, maleic acid, tetrahydrophthalic acid, fumaric acid, itaconic acid,nadic acid, and methyinadic acid. Some suitable anhydrides include, forexample, maleic anhydride, tetrahydrophthalic anhydride, fumaricanhydride, itaconic anhydride, nadic anhydride, and methylnadicanhydride. Maleic anhydride is of particular note.

There are a number of commercially available compounds in which anunsaturated carboxylic acid or unsaturated anhydride has already beengrafted on to a thermoplastic polymer. For example, maleic anhydridegrafted polyolefins like Epolene™ E-43, G-3015, G-3003, C-16, C-18,G-XX01, G-XX15 from Eastman Chemicals, and Polybond™ 3002, 3009, 3150,3200 from Crompton; and, acrylic acid grafted polyolefins like Polybond™1001,1009 from Crompton.

Grafting of an epoxy compound or a coupling agent onto a thermoplasticor elastomeric polymer is often accomplished by using a free radicalinitiator or some form of activating energy (e.g., actinic radiation,heat, etc.). Free radical initiators are well known and one skilled inthe art can readily select an appropriate initiator for the particulargrafting reaction desired. Dialkyl peroxides, such as1,1-bis(t-butylperoxy)-3,3,5-trimethyl cyclohexane or2,5-dimethyl-2,5-(di-ter-butylperoxy)-hexane are examples of one classof suitable free radical initiators. Free radical initiators arepreferably used in an amount of from about 0.1 to about 3.0 parts byweight, more preferably from about 0.5 to about 2.0 parts by weight,based on 100 parts by weight of polymer matrix portion.

The grafting process is usually performed at a suitable temperatureabove the melt or glass transition temperature of the thermoplastic orelastomeric polymer (e.g. about 150-300° C., depending on the chemistryof the polymer) for a sufficient reaction time (e.g. about 5-600seconds, particularly about 30-240 seconds). The grafting process istypically performed in a mixer, such as, for example, in an extruder, aninternal mixer or a sigma blade mixer.

The amount of epoxy compound used in the grafting process is preferablyfrom about 0.1 to about 40 parts by weight, more preferably from about0.3 to about 20 parts by weight, for 100 parts by weight of thethermoplastic or elastomeric polymer. In some cases, initiators likeperoxide compounds must be used together with the epoxy compounds, forexample, in the case of polyolefins. A catalyst may also be used toaccelerate the grafting reaction.

When epoxy compound and coupling agent are both used, the coupling agentis first grafted on to the thermoplastic or elastomeric polymer underconditions as described above. The amount of coupling agent ispreferably from about 0.1 to about 20 parts by weight, more preferablyfrom about 0.2 to about 10 parts by weight, for 100 parts by weight ofthe thermoplastic or elastomeric polymer. Grafting of the epoxy compoundon to the coupling agent-grafted polymer follows via reaction of thefunctional group on the epoxy compound with the functional group on thecoupling agent. The grafting of the epoxy compound is usually performedat a suitable temperature above the melt or glass transition temperatureof the coupling agent-grafted polymer (e.g. about 150-300° C., dependingon the chemistry of the polymer) for a sufficient reaction time (e.g.about 0.5-60 minutes, depending on the chemistry of the epoxy compoundand of the polymer). The weight ratio of epoxy compound to couplingagent may be about 1-40 parts epoxy compound to about 1 part couplingagent.

Generally, during a grafting process, the free radical initiator may bemixed with a thermoplastic or elastomeric polymer before the addition ofepoxy compound or coupling agent, mixed with epoxy compound or couplingagent before combining with a thermoplastic or elastomeric polymer, ormixed with a melt of the thermoplastic or elastomeric polymer and epoxycompound or coupling agent. Contacting the components of the graftreaction is preferably done for a time period sufficient to graft fromabout 10 percent to about 90 percent of the epoxy compound or couplingagent to the thermoplastic or elastomeric polymer. In an extruder, forexample, a residence time of about one to about ten seconds is generallysufficient for the grafting of the epoxy compound or coupling agent ontothe polymer, but this greatly depends on the amount and type of freeradical initiator present.

Other components may be present in the primer. For example,non-epoxidized thermoplastic or elastomeric polymers or mixtures thereofmay be present. Such non-epoxidized polymers may be unreacted reactantsfrom the original reaction, may be additional components or may be acombination of both. The non-epoxidized polymers may be the same ordifferent as the polymer components of the epoxy-modified polymers.Epoxy compounds, for example, unreacted epoxy compounds from theoriginal reaction or additional epoxy compounds may be present.Additional epoxy compounds may be the same or different as theepoxy-containing component of the epoxy-modified polymers. Otheradditives may also be present, for example, oxidation and/or degradationprevention agents (e.g. antioxidants), performance enhancers (e.g.reinforcements, nano-reinforcements, fire retardants, etc.), workabilityenhancers (e.g. pigments, plasticizers, etc.).

In use, the primer composition is applied to a substrate surface as afilm. The film is preferably relatively thin compared to the thicknessof the substrate. The thickness of the film will depend on theparticular application. The film may have a thickness in a range of fromabout 5 μm to about 500 μm, more particularly from about 10 μm to about500 μm, even more particularly from about 30 μm to about 80 μm.

Repair, Insertion, Assembly and Coating of Thermoplastic and/orElastomeric Substrates:

Normally, a thermoplastic or elastomeric substrate is incompatible withtypical materials such as thermoset matrices, some thermoplastic orelastomeric matrices and other materials (e.g. wood, metal, ceramics,etc.) used in the repair, insertion, assembly or coating of substrates,and articles fabricated from substrates. However, the primer of thepresent invention permits convenient repair, insertion, assembly andcoating of thermoplastic and elastomeric substrates with such materials.The primer may be used in any suitable process, for example, in lapshearrepair, scarf butt joint repair, etc. The primer may also be used ininsertion and assembly processes in which a thermoplastic or elastomericsubstrate is bonded to different materials, for example metals, wood,ceramic, leather, fabrics and other composites using commercialadhesives. The primer may also be used in coating processes in which athermoplastic or elastomeric substrate is coated with a coatingmaterial, for example, paint, varnish, etc.

In a typical repair process, a damaged area of a thermoplastic orelastomeric substrate may be removed to expose a fresh surface. Forexample, if the repair is to be done by the butt joint method, a bevelangle of about 2-6°, for example, is made in the area to be repaired. Atbevel angles of 30° or higher, restoration of tensile strength is moredifficult, thus bevel angles of less than 30° are preferred in the buttjoint method. In another example, the repair may be done by the batchjoint method, which is particularly useful when the substrate thicknessis thin (e.g. less than 3 mm). Whichever method is used, the primer isthen applied as a film to the surface of the substrate by any suitabletechnique, for example, by fusion techniques using a heat gun,resistance welding, ultrasonic welding, vibration welding, or molding.

Then, in one aspect, a repair material comprising an uncured thermoset,thermoplastic or elastomeric resin, for example, may be applied directlyon to the primer, for example, by the hand lay-up method, spray-upmethod, injection molding, air-bag molding, vacuum bag molding,compression molding, RTM (resin transfer molding), autoclave,thermo-forming, etc. The resin may then be set to thereby repair thedamaged area of the substrate. In this aspect, the repair materialtypically has good adhesion to the primer. In the case of thermoplasticor elastomeric repair materials, the repair material may be applied as amonomer and subsequently polymerized.

In another aspect, an adhesive may be applied to the primer and a repairmaterial applied to the adhesive. Application techniques as describedpreviously may be used to apply the repair material to the adhesive.This aspect may be used with any types of repair material, for example,cured or uncured thermosets, thermoplastics, elastomers, wood, metal,ceramics, etc. In this aspect, the repair material does not need to havegood adhesion directly to the primer.

In yet another aspect, a thermoplastic or elastomeric substrate, aprimer and a repair material may all be placed together in a mold andmolded together simultaneously. In some instances, the inclusion of anadhesive may be beneficial.

Generally, molding may be done with or without heat, although it isgenerally desirable to mold with heat above the softening temperature ofthe polymeric components. Additionally, molding may be performed atnormal pressure, at high (increased) pressure (i.e. compression) or atlow (decreased) pressure (i.e. vacuum).

All of the above repair techniques may also be easily adapted to theinsertion, assembly or coating of thermoplastic or elastomericsubstrates.

The thermoplastic or elastomeric substrate may be any suitable substratecomprising a thermoplastic or elastomeric polymer as described above.The substrate may be a homopolymer, a copolymer, a blend ofhomopolymers, copolymers or both, a composite of a polymer matrix and areinforcing material, etc. The substrate may be reinforced, for example,by fibers, fillers, layered crystalline clays, whiskers, nanotubes,metallic oxides, metallic sulfides, metallic layered double hydroxides,or mixtures thereof. Fiber reinforcements are of particular interest.

Thermoset resins useful as repair, insertion, assembly or coatingmaterials may be any suitable thermoset matrix, for example, thermosetcomposites, thermoset adhesives, etc. Thermoset composites include, forexample, polyurethanes, epoxy-based composites, vinylesters, polyesters,etc. Thermoset composites may be reinforced, for example, by fibres,fillers, layered crystalline clays, whiskers, nanotubes, metallicoxides, metallic sulfides, metallic layered double hydroxides, ormixtures thereof. Fiber reinforcements are of particular interest.Thermoset adhesives include, for example, epoxy resins, polyurethanes,cyanoacrylates, etc.

Thermoplastic and elastomeric repair, insertion, assembly or coatingmaterials may comprise any suitable thermoplastic or elastomeric matrix,composite and/or adhesive. For example, the thermoplastic andelastomeric polymers and composites described above are suitable. Thesubstrate may be a homopolymer, a copolymer, a blend of homopolymers,copolymers or both, a composite of a polymer matrix and a reinforcement,etc. The material may be reinforced, for example, by fibers, fillers,layered crystalline clays, whiskers, nanotubes, metallic oxides,metallic sulfides, metallic layered double hydroxides, or mixturesthereof. Fiber reinforcements are of particular interest.

Specific coating materials are well known to one skilled in the art andinclude, for example, organic coatings, gelcoats, electrostaticcoatings, paints, varnishes, powder coatings, mixtures thereof, etc. Incoating applications the primer may be applied as a film to the surfaceof a substrate by any suitable technique as described above. The coatingmaterial can then be applied to the primer by any suitable technique,for example, brushing, rolling, dipping, spraying, etc.

The primer of the present invention provides a variety of advantages.For example, in repair methods, the primer is very simple and easy touse so that anyone can use it without a need for specialized training;repair can be done at room temperature without pressure permittingrepair to be done in any setting without specialized equipment; repaircan be done on large parts even in the field; repair is inexpensivewhile permitting great flexibility for different geometric complexities;and a variety of different materials may be used in the repair. Inassembly and insertion methods, the primer may be used in bondingthermoplastic and/or elastomeric substrates to a variety of othermaterials (e.g. other composites, metals, wood, etc.); the primerpermits flexibility in choice of adhesive, large parts may be assembledeven in the field; and, excellent structural joint strength is achieved.Repairs, insertions, assemblies and coatings made using the primer ofthe present invention are resistant to wet and humid conditions as wellas to high and low temperatures. Good bond strength is maintained downto about −30 degrees Celsius and is optimal in the range of about 0-50degrees Celsius.

A variety of articles may be repaired, inserted, assembled or coatedusing methods of the present invention. Such articles include, forexample, sporting goods (e.g. skis, snow boards, snowmobiles, etc.),structural automotive parts (e.g. bumpers, frames, bodies, roofs, doors,etc.), construction parts (e.g. roofs, walls, ceilings, floors, decks,etc.), marine parts (e.g. boat hulls, canoe bodies, etc.), electronicdevices, etc.

For compatibility between the primer and the thermoplastic orelastomeric substrate, it is advantageous to choose a primer with athermoplastic or elastomeric polymer component that is compatible withthe thermoplastic or elastomer of the substrate. In a given instance, itis preferred that the primer be based on a polymer that is the same asor very similar to that of the thermoplastic or elastomeric polymer, orat least one that has a good chemical and/or physical interaction withthe thermoplastic or elastomeric substrate. Matching the thermoplasticor elastomeric polymers increases compatibility between the primer andthe thermoplastic or elastomeric substrate leading to greater bondstrength.

Since the primer also comprises an epoxy-containing component, theprimer will also interact well, for example by chemical reaction orphysical interaction, with functional groups present in the materialused for repair, insertion, assembly or coating or with functionalgroups present in the adhesive if an adhesive is used. When the materialis a thermoset matrix, the epoxy-containing component of the primer mayreact with any aspect of the thermoset matrix, for example, the backbone(e.g. urethane groups of polyurethane or ester groups of polyesters),the hardener (e.g. anhydride, acid, cyanate, amine or amide groups ofthe hardener in epoxy resins), etc. When the material used for repair,insertion, assembly or coating is thermoplastic or elastomeric, theepoxy-containing component of the primer may react with any aspect ofthe thermoplastic or elastomer matrix, for example, the backbone (e.g.amide groups of polyamide or ester groups of polyesters), the end groups(e.g. acid and hydroxy groups in polyesters, amine and acid groups inpolyamides, alcohol or amine groups in functionalised-terminatedrubber), etc. Adhesion is not limited to chemical interaction, but alsoincludes physical interactions between the epoxy-containing componentand the repair, insertion, assembly or coating material that leads tostrong van der Waals interaction and/or hydrogen bonding, etc. It isalso preferred to use a material for repair, insertion, assembly orcoating that more readily interacts with the epoxy-containing componentof the primer. This also leads to greater bond strength.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the invention may be more clearly understood, preferredembodiments thereof will now be described in detail by way of example,with reference to the accompanying drawings, in which:

FIG. 1 is a schematic representation of a lap shear joint configurationin which a primer of the present invention is used to bond athermoplastic polymer substrate to a thermoset composite matrix; and,

FIG. 2 is a schematic representation of a scarf butt joint configurationin which a primer of the present invention is used to bond athermoplastic polymer substrate to a thermoset composite matrix.

EXAMPLES

Abbreviations and Definitions:

PP=polypropylene

MA=maleic anhydride

MAgPP=maleic anhydride graft polypropylene

Twintex™=a glass fiber reinforced polypropylene substrate

GF=glass fibers

Preparation of Primers:

Three different primers comprising epoxy-modified-maleicanhydride-graft-polypropylene (E-MAgPP) were prepared from the reactionof three different epoxy resins with MAgPP. The epoxy resins used wereEpon™ SU-3 (Shell Chemicals), Epon™ 1004 (Shell Chemicals) and Epon™1004 with 5% dioctyl phthalate (DOP-a plasticizer). Epon™ SU-3 is abispehenol A and novolac base epoxy. Epon™ 1004 is a bisphenol A baseepoxy. The MAgPP used was Polybond™ 3150 (Crompton).

Primer 1: Epon™ SU-3 (25 g), Polybond™ 3150 (100 g) and antioxidant (1g) (Igranox™ MD 1024 (Ciba-Geigy)) were reacted in a Brabenderplasticorder mixer at a mixing speed of 60 rpm for 30 minutes at 220° C.to form the primer. The melting point of the resulting Primer 1 wasfound to be 156 ° C., the glass transition temperature was 5° C. and thedegree of crystallinity was 34%.

Primer 2: The same procedure as for Primer 1 was used to prepare Primer2 using Polybond™ 3150 (100 g) and Epon™ 1004 (10 g) with 5% DOP.

Primer 3: The same procedure as for Primer 1 was used to prepare Primer3 using Polybond™ 3150 (100 g) and Epon™ 1004 (20 g) with 5% DOP.

Primer 4: The same procedure as for Primer 1 was used to prepare Primer4 using Epolene™ 3105 (100 g) and Epon™ 1004 (20 g).

Primer 5: The same procedure as for Primer 1 was used to prepare Primer5 using Epolene™ 43 (100 g) and Epon™ 1004 (20 g). Gelation occurredduring the reaction. It is believed that when the concentration ofcoupling agent is as high as that of Epolene™ 43, chemical reactionbetween the epoxy and the coupling agent (maleic anhydride) is difficultto control, leading to the formation of three dimensional networks.

Two different primers comprising epoxy-modified-polyethyleneterephthalate (a thermoplastic polyester) and epoxy-modified-polyamide-6(a polyamide) were prepared from the reaction of epoxy Araldite™ MY 0510(from Vantico) with polyethylene terephthalate (PET) and polyamide-6(PA-6). The PET was PET Eastapak™ 9921 and the PA-6 was UBE 1015B havinga molecular weight of 15 kg/mol.

Primer 6: Araldite™ (4 wt %) was side fed into a Leistritz twin-screwextruder charged with Eastapak™ 9921 (96 wt %) at a rate of 5 kg/h. Thetemperature in all extruder zones was 270° C., the screw speed was 200rpm, the outlet pressure was 250 psi and the residence time was 1.5 min.The screw diameter was 34 mm with L/D of 40.

Primer 7: Araldite™ (4 wt %) and UPE 1015 (96 wt %) were fed into aHaake mini-compounder at a temperature of 240° C. The screw speed was100 rpm and the circulation time was 5 min.

Repair of Twintex™ with Thermoset Composites:

In this Example, the use of a primer of the present invention in therepair of a glass reinforced polypropylene composite (Twintex™) withvarious thermoset resin matrices was explored. The thermoset resinmatrices explored were thermoset composites comprising glass fiberreinforced epoxy (epoxy/GF) or glass fiber reinforced polyurethane(PU/GF). For comparison (referred to as “Reference”, the repair ofTwintex™ with epoxy/GF was also done in the same way without primer).The quality of the repair was evaluated by means of lapshear and scarfbutt joint test methods.

In the lap-shear repair method, a thin film (about 30 μm) of Primer 1was fused to a flat surface of a Twintex™ substrate at a temperatureabove the melting point of the primer (180-200° C.) using a heat gun.The temperature and power level of the heat gun and the time to applythe heat gun on the Twintex™ substrate were controlled to avoidoverheating the thermoplastic composite substrate. A thin film ofpolyimide was introduced on the primer surface before applying the heatgun to avoid having the primer stick to the heat gun. Since the energyprovided by the heat gun was just enough to melt the primer and a thinlayer of the Twintex™ substrate to ensure a good adhesion between them,the primer was cooled very quickly and the film was then released. Athermoset resin was applied to the primed area of the Twintex™ substrateby the hand lay-up method and allowed to set. Referring to FIG. 1, thelapshear joint configuration is illustrated in which the Twintex™substrate (10) is bonded to the thermoset composite (20) with primer(15) in between.

In the scarf butt joint repair method, a damaged area of a Twintex™substrate was removed and a bevel angle of about 6° cut at the area tobe repaired. A thin film (about 30 μm) of Primer 1 was fused to thebeveled surface of the Twintex™ substrate at a temperature above themelting point of the primer (180-200° C.) using a heat gun. A thermosetcomposite was applied to the primed area of the Twintex™ substrate bythe hand lay-up method and allowed to set. Referring to FIG. 2, thescarf butt joint configuration is illustrated in which the Twintex™substrate (100) is bonded to several strips of the thermoset composite(200) with primer (150) in between.

Strengths of the joints formed using Primer 1 in the above methods areprovided in Table 3. Lap-shear strength relates to the strength of thelap-shear joint while tensile strength relates to the strength of thescarf butt joint.

TABLE 3 Thermoset Lap-shear Tensile Composite Strength (MPa) Strength(MPa) PU/GF 11.5 136 Epoxy/GF 13.4 146 Reference 0.5 3

In both the lapshear joint and scarf butt joint repair methods, thepolyurethane and epoxy thermoset composites provided very good results.It is thought that chemical reaction of epoxy groups in the primer withisocyanate groups in the polyurethane composite or with amine groups inthe hardener of the epoxy composite are responsible for the betterperformance. In all cases bond failure was mainly due to failure of theTwintex™ substrate, indicating excellent adhesion between the primer andthe two composites. The scarf butt joint results indicate that repairusing epoxy/GF can restore about 60% of the original tensile strength ofthe Twintex™ substrate while repair with PU/GF can restore about 55% ofthe original tensile strength of the Twintex™ substrate. A better resultfor Epoxy/GF is thought to be due to better interaction between thehardener of the thermoset matrix and the epoxy of the primer.

Similar tests were performed in which the primer was placed in a moldand molded with the Twintex™ prepreg instead of being applied using aheat gun. Similar results were obtained.

The effect of bevel angle on scarf butt joint repair in epoxy/GF repairof Twintex™ using Primer 1 was examined. Table 4 provides results. It isevident from Table 4 that smaller bevel angles provide better bondstrength, presumably due to the increased bonding area and reduced shearstress at the bond line. At a bevel angle of 2°, 60% of the originaltensile strength of the Twintex™ substrate can be restored, as comparedto 20% at a bevel angle of 30°.

TABLE 4 Bevel Angle Tensile Strength (MPa)  2° 168  6° 146 15° 65 30° 50

The effect of temperature on lapshear and scarf butt joint strength wasexamined for epoxy/GF repair of Twintex™ using Primer 1. Table 5provides results. The lap-shear strength relates to lapshear repairwhile the tensile strength relates to scarf butt joint repair using abevel angle of 6°. It can be seen that good bond strength is maintaineddown to a temperature of about −30° C. Above 80° C., bond strengthdeclines, probably due to incompatibility in thermal expansion betweenthe two substrates and the low heat deflection temperature of the PPmatrix of the substrate and of the primer.

TABLE 5 Lap-shear Tensile Temperature (° C.) Strength (MPa) Strength(MPa) −30 9.0 97 0 10.9 113 25 13.4 146 50 11.0 115 80 3.6 38

The effect of moisture on lapshear and scarf butt joint strength wasexamined for epoxy/GF repair of Twintex™ using Primer 1. Joints preparedfrom Twintex™ substrates were exposed to humid (a saturated humidchamber) and wet (immersed in water) environments at temperatures of 50°C. and 95° C. for a period of 48 hours. Table 6 provides results. Thelap-shear strength relates to lapshear repair while the tensile strengthand the tensile modulus relate to scarf butt joint repair using a bevelangle of 6°. It is evident from Table 6 that the bond formed is highlyresistant in a saturated atmosphere (a humid environment) up to 95° C.Tensile strength is more sensitive immersed in water (a wet environment)than tensile modulus or lap-shear strength, but is still quite good. Theresults indicate that repair using a primer of the present invention canbe maintained in humid and wet environments.

TABLE 6 Lap-shear Tensile Tensile Strength Strength Modulus Conditions(MPa) (MPa) (GPa) Ambient 13.4 146 8.2 100% humidity (humid) 10.6 1168.0 50° C. In water (wet) 9.2 91 7.9 50° C. 100% humidity (humid) 9.9112 7.9 95° C. In water (wet) 8.9 40 7.7 95° C.

Assembly of Twintex™ with Epoxy/Glass Fiber Composites:

In this Example, the lap-shear bond strengths of Twintex™ bonded to anepoxy/glass fiber (epoxy/GF) composite using Primer 1 and a commercialepoxy adhesive (30 min Epoxy Lepage) were evaluated. To assemblearticles, a thin film of Primer 1 was fused to a Twintex™ substrate at atemperature above the melting point of the primer (180-200° C.) using aheat gun as described previously. The epoxy adhesive was then applied tothe primer at room temperature and the prepared epoxy/glass fibercomposite was then applied to the adhesive. The adhesive was thenallowed to harden. Table 7 compares the effect of film thickness and theepoxy content used for the preparation of the primer film on lap-shearstrength of the bond formed between the Twintex™ substrate and theepoxy/GF composite.

TABLE 7 Film Thickness Epoxy Lap-shear (μm) Content of Film Strength(MPa) None None 0.3 80 10 wt % (Primer 2) 2.8 30 10 wt % (Primer 2) 6.480 20 wt % (Primer 3) 6.8 30 20 wt % (Primer 3) 13.2 30 20 wt % (Primer4) 13.4

It is evident from Table 7 that the best adhesion occurred when theprimer comprised 20 wt % epoxy and the film thickness was about 30 μm.The lap-shear strength was 13.2 Pa. Since the rupture was located at thethermoset composite surface, it is believed that the bond strength canbe improved if the properties of the thermoset composite are improved.It is also evident from Table 7 that there is no significant differencein the lapshear bond strength of the joints prepared from Primer 3 andPrimer 4.

Assembly of Twintex™ with Metal:

Normally, the hydrophobic nature of a thermoplastic polymer substrateprevents, good adhesion of the substrate to the hydrophilic surface of ametal. In this Example, the lap-shear bond strengths of Twintex™ bondedto a stainless steel using Primer 1 and different commercial thermosetadhesives were evaluated. To assemble articles, a thin film (30 μm) ofPrimer 1 was fused to a Twintex™ substrate at a temperature above themelting point of the primer (180-200° C.) using a heat gun. A thin layerof adhesive was then applied to the primer by hand at room temperatureand the metal was then applied to the adhesive. The adhesive was thenallowed to harden. The adhesives used were Epoxy 5 (an epoxy resin fromLepage), Epoxy 30 (an epoxy resin called Epoxi-Patch™ from DexterCorporation), PU (a polyurethane, self-prepared) and CyaAcry (acyanoacrylate resin called Krazy Glue™ from Elmer Products). Table 8compares the lap-shear bond strengths of the assembled Twintex™-metalarticles.

TABLE 8 Lap-shear Bond Thermoset Adhesive Strength (MPa) Epoxy 5 15.9Epoxy 30 17.2 PU 10.2 CyaAcry 4.4

The lap-shear bond strength of a metal-metal assembly joined using Epoxy30 was 17 MPa. It is evident that the primer of the present inventionpermits excellent bonding of a polypropylene composite to a metal.

Coating of Twintex™:

Primer 1 was molded onto the surface of a Twintex™ substrate bycompression molding. One part of the primed surface was then paintedwith an epoxy-based paint and another part of the primed surface paintedwith an alkyd-based paint using a paint brush. For comparison, anunprimed Twintex™ substrate was coated in part with the epoxy-basedpaint and another part of the unprimed Twintex™ substrate was paintedwith the alkyd-based paint. Both the epoxy-based paint and thealkyd-based paint on the primed surface were impossible to remove, butthe two paints on the unprimed surface were easily removed by hand.

Assembly of Polyethylene Terephthalate and Polyamide-6 with Metal:

In this Example, the lap-shear bond strengths of polyethyleneterephthalate and polyamide-6 bonded to a stainless steel, alone andusing Primer 6 and Primer 7, were evaluated. Table 9 provides thelap-shear bond strengths of the assembled articles.

TABLE 9 Lap-shear Bond Polymer Strength (MPa) PET alone 4.2 PET withPrimer 6 18.6 PA-6 alone 2.6 PA-6 with Primer 7 18.6

It is evident from Table 9 that the use of the primer significantlyincreases the strength of the bond between the polymer and the metal.

Other advantages which are inherent to the invention will be evident toone skilled in the art.

It will be understood that certain features and sub-combinations are ofutility and may be employed without reference to other features andsub-combinations. This is contemplated by and is within the scope of theclaims.

Since many possible embodiments may be made of the invention withoutdeparting from the scope thereof, it is to be understood that all matterherein set forth or shown in the accompanying drawings is to beinterpreted as illustrative and not in a limiting sense.

1. A primer comprising a film of an epoxy-modified polymer comprising anepoxy compound grafted to a polyolefin homopolymer or a polyolefincopolymer consisting of two or more olefin monomers, the epoxy compoundbeing grafted through a coupling agent, the coupling agent comprising anunsaturated carboxylic acid or anhydride, the epoxy compound selectedfrom the group consisting of one or more of diglycidylbutenetricarboxylate, diglycidyl ether of bis-phenol A, diglycidyl etherof p-aminophenol, N,N,N′,N′-tetraglycidyl-4,4′-methylene-bis-benzeneamine, 4-glycidyloxy-N,N′-diglycidylaniline, tetraglycidyl diaminodiphenyl methane, diglycidyl ether of bis-phenol A novolac resin, epoxyphenol novolacs, epoxy cresol novolacs, polynuclear phenolepoxy andhydantoin epoxy.
 2. The primer according to claim 1, wherein the epoxycompound is grafted to polypropylene homopolymer.
 3. A method ofrepairing, inserting, assembling or coating a polyolefin-basedthermoplastic or elastomeric substrate, the method comprising: applyingto the substrate a primer according to claim 1; and, applying a repair,insertion, assembly or coating material to the primer.
 4. The method ofclaim 3, wherein the repair, insertion, assembly or coating materialcomprises a metal.
 5. The method of claim 3, wherein the repair,insertion, assembly or coating material comprises wood or ceramic. 6.The method of claim 3, wherein the repair, insertion, assembly orcoating material comprises a thermoset, thermoplastic or elastomericmatrix.
 7. The primer according to claim 1, wherein the epoxy compoundis grafted to polyethylene homopolymer.
 8. The primer according to claim1, wherein the epoxy compound is grafted to a copolymer of polyethyleneand polypropylene.